Electric discharge tube



March 29, 1949. H. LEMS I ELECTRIC DISCHARGE TUBE Filed Jan. 15, 1946 IN V ENTOR.

UUUUUU ATTORNEY.

Patented Mar. 29, 1949 ELECTRIC DISCHARGE TUBE Hendrik Lems, Eindhoven, Netherlands, assignor,

by mesne assignments, to Hartford National Bank and Trust Company, Hartford, Conn., as

trustee Application January 15, 1946, Serial No. 641,301 In the Netherlands March 14, 1942 Section 1, Public Law 690, AugustS, 1946 Patent expires March 14, 1962 3 Claims 1 The present inventionrelates to electric discharge tubes such as amplifying tubes, electron beam tubes, multiplicator tubes, rectifying tubes and to on and provides an expedient for fixing internal parts of such tubes relatively to a support. To this end, according to the invention, use is made of an insulating adhesive consisting of an inorganic, thermo-lplastic substance.

It has already come to be known to use for this purpose a paste which hardens after having been exposed to the air for some time. For this purpose lead oxide and magnesium oxide mixed with waterglass may be used. The results obtained by means of such substances have not always been satisfactory. In the hardened material cracks may arise due to which the agglutinated parts become detached. In addition this kind of adhesives has the property of releasing considerable quantities of gas after a tube has already been scaled, due to which the vacuum is spoiled.

When according to the invention, the paste is replaced by a suitable thermo-plastic adhesive the said drawbacks are obviated. It will be appreciated that solely those materials can be used whose properties, such as the softening temperature, stability in vacuo, freedom from gases, permit the use in the exhausted discharge space. For this reason glass and enamel are particularly suitable.

Furthermore the adhesives used according to the invention have the advantage that they can be made so soft by controlling the temperature as is desirable in view of the spot where they must be provided. Narrow slits may be filled with them into which a paste can be introduced only with difliculty.

There are tubes, wherein interna1 parts such as electrodes and shields, are secured to rods which are passed through apertures made in the object to be secured to the rods. This construction is found especially in electron beam tubes. In this case it is difficult to establish such a joint that there does not occur displacements along the rod even in the case of shocks. In this case the adhesive used according to the invention may be used with advantage. In a tube thus constructed according to the invention the rods are provided with some amount of play in the holes and the adhesive is provided in the space between the rod and the wall of the aperture in such manner that it adheres both to the rod and to the wall and a firm joint is obtained.

The electrodes may be secured to the rods by means of bushes that are secured to disc-shaped parts of the object to be secured and embrace the 2 rods. When using the present invention it is also advantageous to use such bushes in order to em large the surface of adherence for the adhesive.

Adhesives hardening upon drying in the air have the advantage ofbeing kneadable at the moment at which theyare provided. When using the invention this advantage can be conserved when using for the adhesive a pasty mass containing glasspowder and a mixingliquid. This liquid, for which alcohol or, if required, water may be used disappears upon heating, but the softness remains, since the powder grains are united with eachotherto form a ltiorno'geziccus plastic mass, and even passes over into the state of being thinly liquid at asuflicient temperature. The softness is controlled in such manner that the adhesive spreads over the surface of ad herence without-escaping whereupon the mass is allowed to cool and harden;

It is to be remarked that the well-known use of glass in leading wires through a wall of metal or ceramic material was made in viewo'f sealing in these wireshermetically. The invention provides a solution of another problem viz. supporting parts in the interior'of a discharge tube, where a hermetic seal is not imperative, since the whole is contained in the same space.

The invention will be more fully explained by reference to the accompanying drawing representing by way of example, a part of a discharge tube according thereto.

Fig. 1 is a perspective view of an electrode for an electron beam tube, which is secured to four rods; Fig. 2 is a section of a part of this electrode.

Figure 3 illustrates partly in cross-section a tube embodying the electrode structure according to the invention.

The electrode, a Wehnelt cylinder l closed by a stop 2, is equipped with two cross-shaped fastening plates 3 and 4. In each branch of these plates is provided a round aperture and through these apertures extend four rods 5, B, l and 8 which may consist of hard glass, steatite or another suitable insulating material. By means of bent-over tags 9 metal bushes I0 having tabs l I are secured to the plates 3 and 4 and embrace the rods 5, 6, l and 8 with a small amount of play. The sequence of attachment may be altered at will. Thus, for instance, the closed bushes I0 may first be welded to the plates followed by slipping the rods through them or the plates may first be slipped on the rods followed by bending the bushes around the rods. If desired, the bushes may first be closed and subsequently be welded to the plates or conversely.

At any rate it is advantageous that the bushes l and the plates 3 and 4 surround the rods with a fair amount of play. If the bushes are tightly clamped on the rods the electrodes might readily be slightly displaced which must be prevented. When some space is left the electrodes may be very exactly positioned relatively to each other by means of a templet and when the rods fit exactly in the holes no modification is possible. When the electrodes are provided on the templet the whole is easily slipped on the rods and after the bushes have been closed and secured to the plates 3 and 4, unless this has already been done before, the intermediate spaces are filled with glass or enamel, for instance lead borate glass which has a low softening point and is thinly liquid at a comparatively low temperature. This glass is provided in form of a pasty mass consisting of moist glass powder on the edge of the bush and that of the plate 1. e. at the points indicated by arrows in Fig. 2. By means of a high-frequency magnetic field, a gas flame or the like the plates and the bushes are heated. The heat is transmitted to the pasty filling material, expels the mixing liquid and causes the glass parts to fiow together to form a homogeneous mass. When the temperature is sufiiciently raised the mass becomes thinly liquid so that it penetrates into the intermediate space l2 and fills it completely. By slightly turning the system the mass can be prevented from flowing or dripping down. It is not objectionable that a small quantity of the material passes over the outer wall of the bushes and forms a crust thereon afterwards, for instance at l3. After the filling material has spread well it is allowed to coagulate and now the plates 3 and 4 are rigidly fixed to the rods. The tube shown in Figure 3 comprises within an envelope 20 an electrode assembly 2| in accordance with the invention, said assembly comprising an electrode 1 supported on fastening plates 3 and 4 which are afiixed to rods 5 and l by means of tags 9 and bushes l0, thru the medium of the coagulated filling material l2 all as above described in connection with Figures 1 and 2.

In the same manner also other electrodes such as fccussing electrodes and deflecting plates may besecured. The attachment to rods is of particular importance for tubes having series of electrodes such as, besides the example referred to, secondary-emission photo-cells, rectifying '4 tubes having intermediate electrodes or shields. In all these cases the attachment of the electrodes by means of the adhesive according to the invention can be effected with success.

I claim:

1. A discharge tube comprising an envelope, an electrode within said envelope, a supporting rod for said electrode within said envelope, said electrode having a portion which embraces said supporting rod, and a thermo-plastic insulating material bonding said supporting member and said electrode in fixed insulated relationship.

2. A discharge tube comprising an envelope, an electrode within said envelope having an apertured portion, a rod-like member extending into said aperture in spaced relationship to said electrode, and an insulating inorganic thermo-plastic adhesive material substantially filling the space in said aperture between said member and said electrode, said material adhesively bonding said member and said electrode in fixed relationship.

3. An electric discharge tube comprising an envelope, an electrode within said envelope, a bushing having a tubular portion joined to said electrode, a rod-like member extending through said tubular portion and in spaced relationship therewith, an insulating inorganic thermo-plastic adhesive material bonding said bushing and said portion in fixed relationship and substantially filling the space between said rod-like member and said tubular portion through which said member extends.

HENDRIK LEMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,427,870 Van Keuren Sept. 5, 1922 1,775,218 Thurneyssen Sept. 9, 1930 2,036,652 Smith Apr. 7, 1936 2,056,035 Beggs Sept. 29, 1936 2,138,660 Mann Nov. 29, 1938 2,153,404 White et a1. Apr. 4, 1939 2,193,640 Navias Mar. 12, 1940 2,200,694 Gerecke et al. May 14, 1940 2,202,607 Steudel May 28, 1940 2,296,579 Seelen Sept. 22, 1942 

